books.google.de - Many of the millions of medieval charters surviving in European archives and repositories were written without any reference to a date of issue. The proliferation of undated charters in England and Normandy indicates that the custom was especially peculiar to lands under Norman rule, but charters issued...https://books.google.de/books/about/Dating_Undated_Medieval_Charters.html?hl=de&id=MNNqT5iaPtAC&utm_source=gb-gplus-shareDating Undated Medieval Charters